Orthopaedic surgeons often face the problem where a fractured bone, which appeared completely healed in an X-ray examination refractures during the normal activity of a patient. Ultrasonic methods of determining the degree of fracture healing have also been attempted without much success as a practical test. Therefore, there is an obvious need for a more reliable non-invasive method. Elastic waves in a long bone give rise to a magnetic field generated by the motion of piezoelectrically induced charges. We are in the process of developing an electromagnetic device which can detect this magnetic field and can monitor in-vitro stress waves in bone, without contacting the skin. This overcomes the difficulties encountered in previous wave-propagation and vibration tests in which the results were affected by the properties of the soft tissue over the bone. Id is expected that this device wll be useful as a non-invasive means for: 1) monitoring the rate of fracture healing, and 2) diagnosing other disease states such as osteoporosis. BIBLIOGRAPHIC REFERENCES: Saha, S. and Lakes, R.S. (1977) Development of a non-invasive method for determining in-vivo properties of long bones. Trans. Orthop. Research Soc. 23rd Ann. Meeting, Vol. 2, p. 112. Saha, S. (1977) The relationship between porosity and dynamic strength of human bone. Proceedings of the Third Annual Meeting of the Soc. of Biomaterials and Ninth International Biomaterials Symposium. April 16-19, 1977, New Orleans, La.